The present invention relates to current sources, and in particular, to circuits and methods for calibrating switching current sources.
FIG. 1 illustrates a conventional switching current source 100. Switching current source 100 includes a current source 101, switch 102 (“SW1”), switch 103 (“SW2”), and current source 104. SW1 is responsive to signal S1, and SW2 is responsive to signal S2. Signals S1 and S2 are used to open and close SW1 and SW2. Current source 101 is coupled between a power supply terminal, Vdd, and SW1. Therefore, when SW1 is closed, current (“Ipos”) from current source 101 flows into an output node 110. Similarly, when SW2 is closed, current (“Ineg”) from current source 104 flows out of the output node 110. Signals S1 and S2 are typically generated to control the voltage on output node 110 resulting from currents Ipos and Ineg.
Switching current source 100 may include errors resulting from mismatch in current source 101 and current source 104. Such mismatch may cause corresponding errors in the voltage at the output node 110.